This invention relates in general to manufacture of cast metal wheels and in particular to equipment for handling wheel castings.
Vehicle wheels formed from light weight metal alloy have become quite popular. Such wheels typically include an annular wheel rim that carries a pneumatic tire. The wheel rim has a recessed center portion that facilitates mounting the tire upon the wheel. The inboard and outboard ends of the rim include tire bead seats that support the tire walls. Additionally, radially extending wheel flanges are formed on the ends of the rim to retain the tire upon the wheel.
A circular wheel disc extends across the outboard end of the wheel rim. The wheel disc typically has a central hub that is supported within the rim by a plurality of radially extending spokes. A central pilot hole and a plurality of wheel mounting holes are formed through the wheel hub. The mounting holes are equally spaced about a circle that is coaxial with the pilot hole. The pilot hole is used to position the wheel upon the end of a vehicle axle while the mounting holes receive wheel studs that co-operate with wheel nuts to secure the wheel upon the vehicle. The wheel disc can be cast integrally with the wheel rim to form a one piece wheel.
Manufacturing processes for vehicle wheels are highly automated. Typically, molten metal is poured into wheel molds mounted upon a casting machine. The wheel molds can be mounted upon a rotating carousel to increase casting efficiency. Once the metal solidifies, the casting is removed from the mold and heat treated. The heat treated casting is oversized and requires machining to a final shape and size. The machining is usually accomplished by using multiple work stations. Thus, the wheel casting may first be placed upon a wheel lathe for turning the wheel rim and facing the wheel disc. The wheel casting can then be transferred to a drilling machine for boring the pilot and mounting holes through the wheel hub.
Wheel manufacturing time and costs have been reduced by utilization of robots to move the wheel castings between work stations. Such robots typically have a movable arm that is mounted upon a stationary pedestal. A device for gripping a wheel is mounted upon the end of the robot arm. The wheel gripper device securely grasps an end of the wheel rim. The arm then swings and elevates while contracting or extending to move the wheel casting between work stations.
Referring now to the drawings, there is shown in FIG. 1 an end view of a finished vehicle wheel 10 held by a prior art wheel gripper device 12. The wheel gripper device 12 includes a pair of opposed arms 14. The arms 14 are moveably mounted on the end of a conventional robot arm 13 and can be moved toward and away from each other, as illustrated by the small double headed arrows in FIG. 1. As best seen in FIG. 2, a bracket 15 is mounted upon the end of each of the arms 14. In FIG. 2, the gripper 12 is illustrated with a wheel casting 18 that includes inboard and outboard wheel tire bead retaining flanges, 20 and 22, respectively. The casting 18 is shown in section with the finished machined shape of the wheel outlined by dashed lines. Each of the brackets 15 includes a body 16 that is attached to an end of one of the arms 14. A single roller 24 is rotatably mounted upon an end of each of the bodies 16. A V-shaped groove 26 is formed in the circumference of each of the rollers 24.
During operation, the gripper arms 14 are extended until the rollers 24 enter the plane of the inboard casting wheel flange 20. The gripper arms 14 are then contracted toward one another causing the V-shaped grooves 26 in the rollers 24 to receive the edge of the flange 20. The rollers 24 rotate as needed to position the arms 14 relative to the casting 18. The arms 14 continue to contract toward one another until the casting 18 is securely clamped between the rollers 24. The robot arm 13 then moves to position the casting 18 upon a wheel lathe chuck (not shown). The wheel lathe chuck clamps onto the casting 18, whereupon the gripper arms 14 are extended away from one another to release the casting 18. The robot arm 13 withdraws the gripper arms 14 and brackets 15 from the casting 18. The wheel lathe then proceeds to turn the wheel rim and face the wheel disc to final shape and size.
Once the wheel lathe operations are completed, the robot arm 13 removes the casting from the lathe chuck by gripping the outboard wheel flange 22, as illustrated in FIG. 3. Components shown in FIG. 3 that are the same as components shown in FIG. 2 have the same numerical identifiers. The robot arm 13 then removes the casting 18 from the wheel lathe and transports the casting 18 to a drilling machine for boring the pilot and mounting holes. The robot arm 13 positions the casting 18 upon the drilling machine. After the casting 18 is mounted upon the drilling machine, the arms 14 are extended from one another to release the casting 18. The robot arm 13 is again withdrawn. When the drilling operations are completed, the robot arm 13 removes the machined wheel from the drilling machine and moves it to the next work station.
This invention relates to improved equipment for handling wheel castings.
When a wheel casting is heat treated, the thinness of the wheel rim may allow the inboard end of the rim to distort. As a result, it is difficult to consistently load wheel castings onto a wheel lathe chuck by gripping the inboard end of the casting rim such that the wheel casting is coaxially mounted upon the chuck. Accordingly, the concentricity and static imbalance of the resulting wheel can be degraded. Because the outboard end of the wheel casting rim includes a portion of the wheel disc, it is thicker and retains circularity better than the inboard end of the rim during heat treatment. Accordingly, it would be desirable to grip the wheel castings by the outboard wheel flange for loading onto the wheel lathe chuck.
The present invention contemplates an improved gripper bracket having a bracket for gripping a wheel that includes a body that is adapted to be mounted upon a robot arm. A pair of rollers are rotatably mounted upon opposite ends of the body. The bracket body is symmetrical about a plane that passes transversely through the center of the body. Also, each of the rollers has a groove formed in the circumference thereof. In the preferred embodiment, the roller groove has a V-shape. Additionally, the bracket has a recess formed therein that is adapted to receive the robot arm.
The invention also contemplates a device for clamping onto and transporting a vehicle wheel that includes a pair of spaced apart arms adapted to be movably mounted upon an end of a robot arm. The device also includes a plurality of brackets, with a bracket mounted transversely upon each end of each of the spaced apart arms. A pair of rollers are mounted upon each of the bracket bodies with one of the pair of rollers mounted upon each end of each of the bracket bodies. Each of the rollers lies in one of two spaced apart planes that are parallel to the spacer arms. The arms are movable relative to a wheel casting for the rollers to contact a portion of the wheel casting and clamp the wheel casting therebetween.